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Exchange Tower in Detroit upends modular construction.
The Exchange tower in Detroit, a “top-down” skyscraper, is in the final stages of completion. The building, which is 63 m tall, is a testament to an advanced modular construction technique. Its floors were each prefabricated on the ground and then lifted and installed from the top down using central spines. (main pic: Liftbuild’s modular-built top-down skyscraper in Detroit. Liftbuild/Barton Marlow.)
Liftbuild, the company behind the construction, utilised a hyper-modular version of the lift slab technique that dates back to the 1950s. In this latest iteration, the process works as follows: first, the foundations are prepared and central spines are erected, containing stairs and elevators, to the full height of the building.
Each floor, starting with the roof, is built close to the ground, including the steel frame, concrete slab, facade, flooring, walls, electrical systems, plumbing, fire protection, ducting, and more. Liftbuild coordinates with various contractors to ensure that as much work as possible is done on the ground, creating a factory-like assembly area where prefabricated parts are installed and lifting is minimised. Any work that needs to be done under the slab can be accomplished by lifting the entire structure using jacks around the spines.
When each 453 metric tonne floor is ready, it’s lifted to the top of the spines using eight strand jacks, with the upper floors taking about 10 hours to lift. The floors are then permanently secured to the spines using a proprietary bolted connection.
Each floor is a cantilevered design supported solely by the two spines, resulting in unobstructed views from the residents’ windows. There are no interior walls or columns, allowing designers to have complete creative freedom with each floor’s layout.
Barton Marlow, Liftbuild’s parent company, led the design and construction and also funded the project as a demonstration of its capabilities. The company claims that the technology will greatly improve worker safety, as once the spines are in place, there is no need for workers to be at heights or hanging from ropes on the exterior. Additionally, the company states that the method will result in cheaper and faster construction, using fewer workers, with cost savings of up to 20% and time savings of up to 50%.
As of late January, all the liftable floors have been lifted and secured, with only the two bottom floors remaining to be built using conventional methods.
Liftbuild’s Chief Operating Officer, Joe Benvenuto, stated: “We are very pleased with the outcome of our first proof of concept for the Liftbuild technology. The implementation of our proprietary methods has produced the advantages we expected, and we are confident that the results at the Exchange Building will set the stage for a broader commercialization of Liftbuild.”
The company is now focusing on its next opportunity to deploy the technology, with the goal of delivering increased safety, labour efficiencies, and reduced schedules for project stakeholders.
